Evans posted the letter but later regretted it, and tried unsuccessfully to retrieve the letter from the postman, and Mr Laws received it on September 6 last year.
"The content of the letter was threatening and threatened to expose Mr Laws in terms of his personal life,'' said Judge David Cameron.
"It contained a threat to expose these matters by way of national newspapers and television channels. He also indicated he would attend public meetings to expose Mr Laws.
"It directed Mr Laws to withdraw from his mayoral campaign or these threats would be put into action.''
Evans was arrested three days after Mr Laws - a current Wanganui District Council and Whanganui District Health Board member - received the letter. While being questioned by police Evans handed over a second letter he had written to Mr Laws but had not posted, which contained similar material.
"The crown do not rely on that letter save to the extent that it shows an ongoing animosity,'' said Judge Cameron.
Evans has previous convictions ranging from 1981 to 2012 which Judge Cameron called "disturbing''.
They included using offensive language, speaking threateningly, and offensive use of a telephone. He had also been imprisoned for violence and dishonesty charges, and had previous drink driving convictions.
"It's everybody's democratic right to stand for public office,'' said Judge Cameron.
"This letter was calculated to prevent just that.''
He sentence Evans to six months' home detention with a 12 month post detention order of non-association with Mr Laws and Ms Severinson.
